Method of continuous rotary casting of metal utilizing a liquefied gas to facilitate solidification

ABSTRACT

Rotary method of continuously casting metallic articles in which a liquefied gas is introduced into the top of the mold and apparatus for use in carrying out said method.

United States Patent 11 1 V 1111 3,776,295 Mola et al. Dec. 4, 1973 METHOD OF CONTINUOUS ROTARY [56] References Cited CASTING QF METAL UTILIZING A UNITED STATES PATENTS LIQUEFIED GAS To FACILITATE 2,963,758 12/1960 Pestel et al. 164/49 X SOLIDIFICATIQN 3,395,750 8/1968 Keene 164/259 [75 inventors: Michel Mola, Paris; i pp 3,545,529 12/1970 Keene 164/66 X Barfllelemy, Sevres; Gerard 39ml FOREIGN PATENTS OR APPLICATIONS i' Jean Gale)" 308,044 9 1955 Switzerland 164/49 samtMau" France 439,602 12/1968 Switzerland 164/84 Societe Civile DEtudes De Centrifugation, Paris, France Dec. 22, 1971 Assignee:

Filed:

App]. No.: 210,712

Borgign Application Priority Data Dec. 24, 1970 France ..7046640 US. Cl 164/66, 164/73, 164/82 Int. Cl B22d 11/10 Field of Search 164/49, 66, 82, 84,

Primary Examiner-11. Spencer Annear AttorneyJoseph F. Brisebois et a1.

[57 ABSTRACT 11 Claims, 4 Drawing Figures PATENTEUUEC 4 I975 SHEET 10F 2 PATENTED DEC 4 1915 SHEET 2 OF 2 METHOD OF CONTINUOUS ROTARY CASTING OF METAL UTILIZING A LIQUEFIED GAS TO FACILITATE SOLIDIFICATION SUMMARY OF THE INVENTION This invention relates to a new continuous rotary method of casting metallic articles, and in particular casting steel in the form of solid cylinders or hollow cylindrical tubes.

There is a known method of continuously casting cylindrical steel articles by introducing liquid steel into a cooled mold, which rotates about a vertical axis, with the article produced being extracted downwardly while being rotated at the same speed as the mold.

However, it is relatively difficult to produce perfect metal in the central part of solid metallic castings when operating at high extraction speeds (for example, of the order of 2 meters per minute for castings having diameters of the order of 130 to 150 mm). The defects produced in the central part of the castings are due in part to shrinkage holes which result during solidification and in part to inclusions of slag or other impurities. They often make the casting unacceptable, especially when the castings are to be used for making steel tubes of high quality.

It has already been suggested that solid castings be produced from steel by a continuous rotary casting method in which the jet of molten metal is positioned in a particular manner which substantially reduces the aforesaid defects. Nevertheless it remains desirable to completely eliminate all the shrinkage holes and inclusions which remain in the center of the casting.

It has also been suggested that hollow round castings be produced by introducing liquid metal into a rotating mold which is provided with a central mandrel so as to simultaneously form two solid concentric metallic skins between which the tubular casting is formed.

Despite all the improvements which have been made in this type of process, it is still true that, in certain cases, the inner skin of the tubular casting has defects which are due to inclusions of slag or other impurities near this skin, and which are very undesirable when a steel tube of high quality is to be made.

This invention relates to a process which makes it possible to improve the quality of metallic castings either in their central portions when the castings are solid, or near their inner skins in the case of hollow castings.

It is an object of the present invention to provide a new process for the continuous manufacture of metal castings, particularly steel castings, by continuously pouring a jet of liquid metal into a cooled mold, with the liquid metal contained in the mold turning about a vertical axis, while the casting is vertically and downwardly extracted, characterized by the fact that an inert liquefied gas is introduced into the top of the mold near the surface of the liquid metal.

In a preferred embodiment of the invention the mold, the casting being manufactured, and the liquid metal being solidified, are simultaneously rotated about a vertical axis, preferably at the same speed.

In another embodiment, the mold and the solidified portion of the casting are not rotated, in contradistinction to the metal which has not yet been solidified, which is rotated by the impact of the jet of liquid metal on the unsolidified upper part of the casting and/or by a rotating electromagnetic field induced in the unsolidiinvention liquefied gas is applied to the surface of the metal while it is solidifying at a point to which the liquid metal is brought as a consequence of the rotation of the mold after it has been introduced into the mold.

In accordance with a preferred method of carrying out the invention the liquid metal is brought to an eccentric position with respect to the mold by directing the jet of metal in the direction of rotation of the mold, and the liquefied gas input is also eccentrically positioned downstream of the liquid metal input with respect to the direction of rotation of the mold.

The quantity of liquefied gas which, according to the invention, may be directed against the surface of the bath of liquid metal may vary within wide limits. It depends especially on the diameter of the mold in which the metal is being solidified.

It may be said that the maximum suitable supply of liquefied gas corresponds to the quantity which it is possible to introduce without disturbing the surface of the bath of liquid metal, and in particular without producing bubbles on that surface.

In effect, when an increasing supply of liquefied gas is introduced, no modification of the state of the surface of the liquid metal is at first noted, whereas when a certain rate of supply is exceeded, bubbles appear which increase in quantity and constitute a clearly undesirable phenomenon from the point of view of obtaining metallic castings of good quality.

Moreover, the minimum quantity of liquefied gas which must be supplied to the surface of the liquid bath may be estimated by determining the moment at which the black fumes which result from the introduction of lubricating oil into the mold cease to become visible.

It is known, in effect, that it is conventional, when continuously casting steel, to introduce a small quantity of oil, and especially a vegetable oil such as rape oil, and that the precipitation of this oil onto the steel in the course of fusion has the effect of producing a black smoke which disappears when a sufficient quantity of liquid gas according to the invention is introduced.

In most cases, in accordance with the invention, from 0.08 to 0.5 liters .per minute per square decimeter of section of the rotating mold should be supplied to the surface of the metallic bath being solidified. A supply of liquefied gas of the order of 0.3 liters per minute per square decimeter of section usually gives good results.

In a preferred embodiment of the invention the liquefied gas is introduced at a point in the mold which is downstream, with respect to the direction of rotation,

from the point at which the liquid metal is introduced,

and upstream from the point at which the lubricating oil is introduced.

As a first consequence of this invention it will be noted that it is possible to reduce by about 50 percent the quantity of lubricating oil which is required.

The introduction of liquefied gas according to the invention also has the effect of considerably reducing the quantity of slag and other impurities which are normally brought to the surface of the liquid bath.

This may be readily observed since when pouring solid round castings in accordance with conventional methods it is necessary to recover by means of a rod the slag which assembles at the center of the paraboloid. If in accordance with the invention, liquefied gas is introduced, it is no longer possible to observe and recover the smallest amount of slag from the surface of the bath.

The process according to the invention makes it possible to obtain castings of better quality substantially free from the defects which, in conventional processes, occur in the central part of solid castings or in the internal surfaces of hollow castings.

It is remarkable that this result is obtained by the combination of introducing a liquefied inert gas and rotating the casting which is characteristic of the invention.

In effect, comparative tests in which an inert gas is supplied, and in particular gaseous nitrogen, have shown that they do not result in the desired end.

Moreover, the fact that the process is applied to a continuous rotating casting makes it possible to obtain excellent distribution of the liquefied gas at the moment it comes in contact with the surface of the bath and impart the best quality to the casting in the course of formation.

It is remarkable to note that the analyses which have been made have not shown any increase in the nitrogen content of the steel cast by the process according to the invention, despite the fact that nitrogen has been used as the liquefied gas.

When liquefied gas is supplied without rotating the mold, the fact that the liquefied nitrogen always strikes the same point on the surface of the metal being solidified results in the absorption of nitrogen by part of the metal and this is generally considered unacceptable.

It is a further object of the present invention to provide the new article of manufacture which consists of an installation for the continuous rotary casting of metallic articles, of the type comprising a cooled mold rotating about a vertical axis, means for extracting the casting which rotate about the same vertical axis, means for spraying a cooling fluid against the casting leaving the mold and a device for supplying liquid metal at the top of the mold, characterized by the fact that it also comprises a preferably cooled device for supplying a flow of liquefied gas to the surface of the liquid metal.

It is a further object of the present invention to provide the new article of manufacture which consists of an installation for the continuous rotary casting, of metallic articles of the type comprising a cooled rotating mold, non-rotating means for extracting the castings, means for cooling the castings, a device for supplying a liquid metal to the upper part of the mold, and means such that the impact of the jet of liquid metal and/or electromagnetic fields cause rotation of the liquid metal being solidified inside the unsolidified portion of the casting, characterized by the fact that it also comprises a preferably cooled device for supplying a flow of liquefied gas to the surface of the bath of metal liquid.

In a preferred embodiment of the invention, the device comprises three pouring spouts arranged in the following order with respect to the direction of rotation:

. a spout for supplying liquid metal, a spout for supplying liquefied gas, and a spout for supplying lubricating oil to the mold.

In order that the invention may be better understood two embodiments thereof will now be described, purely by way of illustration and example, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view, partially in section, showing a device for use in carrying out the invention;

FIG. 2 is a top plan view of the device shown in FIG.

FIG. 3 is a sectional view taken along the line III-III of FIG. 4, showing another embodiment of the invention for use in casting hollow articles; and

FIG. 4 is a top plan view of the device shown in FIG. 3.

FIG. 1 schematically shows a mold l which is cooled by water circulating in the space 2, and within which the solid cylindrical casting 3 is beginning to solidify.

The mold l is rotated about its vertical axis in the direction of the arrow F by conventional apparatus not shown. FIG. 1 also schematically shows the means for spraying water 4, which cools the casting once it has dropped below the bottom of the mold 1.

Finally, the lower part of FIG. 1 schematically shows the extracting rollers S, which draw the casting down, and are rotated about their own axes and about the axis of the casting at the same speed as the mold rotates, as is also schematically indicated on the drawing by arrows. At the upper end of the mold a nozzle 6 projects a jet of liquid steel onto the upper surface of the casting at a point which is eccentric with respect to its axis.

The drawing also shows the cooled duct 8 which supplies the liquefied gas in the form of a small jet 9.

Finally the drawing shows the duct 10 which supplies a small quantity of lubricating oil 11, for example rape oil.

FIG. 2 shows the members which are situated at the top of FIG. 1 including the supply spouts for the liquid steel 7, on the one hand, and the liquefied gas 9, on the other hand, and finally the lubricating oil 11 are, in the preferred embodiment of the invention, directed in the direction of rotation of the mold, and are so positioned the jet of metal is upstream, whereas the jet of lubricating oil is downstream, with respect to the jet of liquefied gas.

In one specific method of carrying out the invention a mold 2 is used which has an internal diameter of mm and produces in a continuous manner a solid steel casting having substantially the same diameter, which is drawn downwardly at a linear speed which may be between 1.8 meters and 2.20 meters per minute. In accordance with the invention, a supply of liquefied nitrogen is introduced through the duct 8 at the rate of between 0.3 and 0.5 liters per minute. It suffices to supply rape oil at a rate of the order of 5 to 6 cm per minute, which corresponds to substantially half the quantity which is necessary if no liquid nitrogen is used in accordance with the invention.

FIGS. 3 and 4 show the parts corresponding to those shown in FIGS. 1 and 2 respectively, in the case of a device for pouring hollow castings 3'.

In the embodiment illustrated in FIGS. 3 and 4 the spouts supplying liquid metal liquefied gas and lubricant are also shown and distributed at substantially regular intervals about the periphery of the mold. Inside the rotating mold 2 is a mandrel 12 which is also rotated about its vertical axis by means not shown, and

which is also cooled in a conventional manner by water circulating inside it.

This device makes it possible to provide at the level of the mold two skins of concentric solidified metal between which the liquid metal constituting the hollow casting becomes solidified. The other characteristics of the embodiment which has been hereinbefore described are also found in this embodiment. The apparatus according to the invention makes it possible to produce metallic castings and in particular steel castings which have particularly satisfactory internal surfaces.

It will of course be appreciated that the embodiments and methods which have just been described have been given purely by way of illustration and example and may be modified as to detail without thereby departing from the basic principles of the invention. In particular, it is clear that the point at which the liquefied gas is introduced into the mold is not necessarily the one which has been described in the illustrated embodiments even though these are the preferred embodiments.

In like manner, it is clear that, without departing from the basic principles of the invention, liquefied gases other than nitrogen might be used to the extent that these gases are inert with respect to the metal which is being used.

With respect to the nature of the metal which may be cast in accordance with the invention, this is not limited to steel, but the process according to the invention may also be applied to all metals or alloys having similar general characteristics, in particular similar characteristics with respect to its temperature and conditions of solidification.

What is claimed is:

1. Method for the continuous rotary casting of metallic articles by introducing a jet of liquid metal into the top of a cooled mold within which the unsolidified metal rotates about a vertical axis while the casting is vertically downwardly extracted, which comprises the step of introducing a liquefied gas which is inert with respect to the metal at the top of the mold adjacent the surface of the liquid metal.

2. Process as claimed in claim 1 in which the casting being manufactured and the liquid metal being solidified are simultaneously rotated about a vertical axis at approximately the same speed.

3. Process as claimed in claim 1 in which the mold and the solidified portion of the casting are not rotated, but the unsolidified portion of the metal is rotated with respect to the solidified portion thereof by the impact of the jet of liquid metal on the unsolidified upper surface of the casting.

4. Process as claimed in claim 1 in which the mold and the solidified portion of the casting are not rotated, but the unsolidified portion of the metal is rotated with respect to the solidified portion thereof by a rotating electromagnetic field induced in the unsolidified metal.

5. Process as claimed in claim 1 in which the liquefied gas is nitrogen.

6. Process as claimed in claim 1 in which the liquefied gas is argon.

7. Process as claimed in claim 1 in which the liquefied gas is supplied to the surface of the metal being solidified at a point to which the liquid metal is brought by rotation of the mold after having been deposited in said mold. i

8. Process as claimed in claim 1 in which the liquid metal is supplied at a point eccentric with respect to the axis of the mold and the liquefied gas is also eccentrically supplied downstream of the point of supply of liquid metal with respect to the direction of rotation of the mold.

9. Process as claimed in claim 1 in which the liquefied gas is supplied to the surface of the bath of metal being solidified at the rate of between 0.08 and 0.5 liters per minute per square decimeter of section of the mold.

10. Process as claimed in claim 9 in which the liquefied gas is supplied at the rate of about 0.3 liters per minute per square decimeter of section of the mold.

11. Process as claimed in claim 8 in which the liquefied gas is supplied at a point upstream of a point at which lubricating oil is supplied. 

1. Method for the continuous rotary casting of metallic articles by introducing a jet of liquid metal into the top of a cooled mold within which the unsolidified metal rotates about a vertical axis while the casting is vertically downwardly extracted, which comprises the step of introducing a liquefied gas which is inert with respect to the metal at the top of the mold adjacent the surface of the liquid metal.
 2. Process as claimed in claim 1 in which the casting being manufactured and the liquid metal being solidified are simultaneously rotated about a vertical axis at approximately the same speed.
 3. Process as claimed in claim 1 in which the mold and the solidified portion of the casting are not rotated, but the unsolidified portion of the metal is rotated with respect to the solidified portion thereof by the impact of the jet of liquid metal on the unsolidified upper surface of the casting.
 4. Process as claimed in claim 1 in which the mold and the solidified portion of the casting are not rotated, but the unsolidified portion of the metal is rotated with respect to the solidified portion thereof by a rotating electromagnetic field induced in the unsolidified metal.
 5. Process as claimed in claim 1 in which the liquefied gas is nitrogen.
 6. Process as claimed in claim 1 in which the liquefied gas is argon.
 7. Process as claimed in claim 1 in which the liquefied gas is supplied to the surface of the metal being solidified at a point to which the liquid metal is brought by rotation of the mold after having been deposited in said mold.
 8. Process as claimed in claim 1 in which the liquid metal is supplied at a point eccentric with respect to the axis of the mold and the liquefied gas is also eccentrically supplied downstream of the point of supply of liquid metal with respect to the direction of rotation of the mold.
 9. Process as claimed in claim 1 in which the liquefied gas is supplied to the surface of the bath of metal being solidified at the rate of between 0.08 and 0.5 liters per minute per square decimeter of section of the mold.
 10. Process as claimed in claim 9 in which the liquefied gas is supplied at the rate of about 0.3 liters per minute per square decimeter of section of the mold.
 11. Process as claimed in claim 8 in which the liquefied gas is supplied at a point upstream of a point at which lubricating oil is supplied. 